Question

A concave lens of focal length 25cm and a convex lens of focal length 20cm are placed in contact with each other . What is the power of combination ? Also , Calculate focal length .

Class - 10th
Chapter - Light , Reflection and Refraction .

Kindly don't spam ​

Answer 1

Answer:

f1 = 25 cm = 0.25 m

p1 = 1/f1 = 1/0.25 = 4D

f2 = -10 cm = -0.1m

p2 = 1/f2 = 1/-0.1 = -10D

(a) Power of the combination:

P = p1 + p2

= 4D + (-10D)

= - 6 D

(b) Focal length of the combination:

f = 1/P = 1/-6 = -0.1666m = -16.66cm

(c) The combination has negative focal length, so it is diverging.

Explanation:

can you please mark mine as brainlest please .

Answer 2

$\huge{ { \underbrace{ \mathbb{ \red{QuEsTiOn \ }}}}}$

A concave lens of focal length 25cm and a convex lens of focal length 20cm are placed in contact with each other . What is the power of combination ? Also , Calculate focal length .

$\huge{ { \underbrace{ \mathbb{ \red{AnSwEr\ }}}}}$

${ { \underbrace{ \mathbb{ \red{GiVen\ }}}}}$

$focal\: length\: of \:concave\: lens(f_1)=25cm$

$focal\:length\:of\: convex\:lens(f_2)=-20cm$

${ { \underbrace{ \mathbb{ \red{To\:PrOvE\ }}}}}$

$A) \:Focal \:length (f)$

$B) \:The\: power\: of \:combination (P)$

${ { \underbrace{ \mathbb{ \red{SoLuTiOn \ }}}}}$

$\huge {A) \:Focal \:length (f)}$

$\frac{1}{f}=\frac{1}{f_1}+\frac{1}{f_2}$

$Substitute\: the\: values$

$\frac{1}{f}=\frac{1}{25}+\frac{1}{-20}$

$\frac{1}{f}=\frac{1}{25}-\frac{1}{20}$

$\frac{1}{f}=-\frac{1}{100}$

${\boxed {\boxed {f=-100cm}}}$

______________________________________

$\huge {B) \:The\: power\: of \:combination (P)}$

${\boxed {\boxed {P=\frac{1}{f_1}+\frac {1}{f_2}}}}$

$P=\frac{1}{0.25}+\frac {1}{-0.20}$

$P=\frac{100}{25}-\frac {100}{20}$

$P=\frac{400-500}{100}$

$P=- \cancel \frac{100}{100}$

${\boxed {\boxed {P=-1D}}}$

$\therefore combination\: is\: diverging$

$\blue{\boxed{\blue{ \bold{\fcolorbox{red}{black}{\green{Hope\:It\:Helps}}}}}}$

${\mathbb{\colorbox {orange} {\boxed{\boxed{\boxed{\boxed{\boxed{\colorbox {lime} {\boxed{\boxed{\boxed{\boxed{\boxed{\colorbox {aqua} {@suraj5069}}}}}}}}}}}}}}}$